This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Helices are not only ubiquitous in proteins, but are also known to sample a wide variety of sequences. However, previous experimental studies on the folding dynamics of monomeric alpha-helices have focused mainly on alanine-based peptides. Since such alanine-rich sequences are rarely encountered in proteins, it is thus imprudent to assume that naturally occurring alpha-helices would show similar folding rates as those of alanine-rich peptides. In light of the important role of secondary structure formation in existing protein folding models, there is a strong need for further investigation of the sequence-dependence of alpha-helix folding kinetics. Herein, we study the relaxation kinetics of a naturally occurring alpha-helix peptide derived from a helical protein as well as a designed helical peptide that is stabilized by salt-bridges, in response to a laser-induced T-jump using infrared (IR) spectroscopy. The goal of this project is to provide further insights into the folding mechanism of alpha-helices and the kinetic role of sidechain-sidechain interactions.